Screening for cervical cancer, by means of the Pap smear, has demonstrably reduced the burden of cervical cancer among women of reproductive ages. Unfortunately, in women beyond the reproductive years the usefulness of cervical screening is uncertain. We propose to evaluate the efficacy of cervical screening in older women using a case-control study design. We will compare the prior use of the Pap smear in two groups of older women (55-79 years of age) enrolled at one of two, large, health maintenance organizations in the northwestern United States. The overall goal of this proposal is to assess, in older women, the degree to which screening of the uterine cervix, by means of a Pap smear, can reduce the incidence of cancer of the cervix. The specific aims are: (1) to determine the incidence of invasive cervical cancer in older women following a negative screening exam; and (2) to compare older women who develop invasive cervical cancer and an otherwise similar group of women without this condition for a history of cervical screening. Cases will consist of those women who developed invasive cervical cancer during 1980-1997 while enrolled at either Group Health Cooperative or Kaiser Permanente Northwest. Eligibility will be restricted to women with seven years of continuous enrollment. For each case, three controls will be randomly sampled from enrollees who have not previously had a hysterectomy and matched to cases on age and duration of enrollment in the health plan. Medical records of the study subjects will be reviewed to ascertain receipt of Pap smear screening and other information relevant to the risk of developing cervical cancer (i.e., smoking). Cases and controls will be compared for a history of screening during the pre-invasive detectable phase of the tumor. To the extent that screening leads to a reduced incidence of cervical cancer in this population, a history of screening - during the time period in which the precursor lesion is present, but prior to the development of cancer - will be more common in controls than cases. The results of the proposed study should provide a more solid basis either for recommending continued (or expanded) cervical screening of older women, or instead for a reduced level of screening and an allocation of the cost savings to more productive means of health promotion.